1. Field of the Invention
This invention relates to accumulating conveyor systems. More particularly, this invention relates a metering mechanism or assembly for separately advancing parts on an accumulating conveyor in order to space the parts out on the conveyor and in some instances to directly discharge the parts from the conveyor.
2. Description of the Prior Art
In an accumulating type conveyor, parts are advanced, usually in a single row, in a step by step manner. The parts accumulate or stack up in abutting relationship at a discharge point or at the end cf the conveyor. In particularly long conveyors, the stacking up of a great number of parts can tend to overload the discharge or other handling mechanism and can cause damage to and jamming of this mechanism. With each step by step movement, the forward thrust of the abutting parts is transmitted to act against the discharge or other orienting mechanism.
A widely accepted type of accumulating conveyor is known as a lift and carry or walking beam conveyor. One such conveyor of an advanced design is described in U.S. Pat. No. 4,838,411. The conveyor of this patent utilizes a pair of elongated, spaced apart and parallel stationary rails. A pair of movable rails are located between the stationary rails and move from a point below to a point above the rails, and from a retracted position to an advanced or forward position. Thus parts resting on the stationary rails are picked up by the movable rails and moved forward to a point where they are again lowered to a resting position on the stationary rails. This type of conveyor is particularly adapted for use in conveying conventional parts which extend above the rails and also elongate parts which extend between the rails. For example, automotive connecting rods can be conveyed with or without a cap attached to the beam while the beam extends between the rails, or the cap can be conveyed alone supported entirely above the rails. In either mode, the accumulation of abutting parts causes considerable force to be exerted against a device at the end of the conveyor which is attempting to discharge the parts one at a time.
Many solutions to this problem of excessive longitudinal force transmission in accumulating conveyors have been advanced and used with varying degrees of success and having varying disadvantages. In longer conveyor systems, the conveyor can be divided into separately operating segments which break up or limit the number of parts which can accumlate at the discharge point. This requires portions of the conveyor to remain idle for periods of time and then be operated to catch up the flow of parts. This in turn, results in a slower overall operating rate.
Other systems may use staking mechanisms which employ a tapered pin which is driven between abutting parts to cause separation. This can involve a considerable degree of complexity in sensing the contacting faces of the parts so that the stake pin passes between parts and does not directly impact a single part. Even with good synchronization, scratching or marring of the parts by this type of separation or discharge mechanism can be unsatisfactory, particularly for many parts such as the above mentioned engine connecting rods.